Polarization conversion element, polarization illuminator, display using the same illuminator, and projector

ABSTRACT

A polarizing conversion device in accordance with the invention includes a first optical element for condensing an incident beam and forming a plurality of intermediate beams spatially separated from one another, and a second optical element for spatially separating each intermediate beam into two polarized beams and aligning the polarization directions of the polarized beams, thereby obtaining the same type of polarized beams. In the second optical element, a shading plate is placed to prevent light from directly entering a section corresponding to a reflecting plane of a polarizing separation unit array. Since the ability of separating the intermediate beam into two polarized beams is thereby enhanced, it is possible to perform conversion into the same type of polarized beams polarized in the same direction, with high efficiency.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polarizing conversion device and apolarizing illumination device for generating, from incident light beamsas randomly polarized beams, illuminating beams that have a more uniformlight intensity distribution in an illumination region than that of theincident beams and are polarized in almost the same direction.Furthermore, the present invention relates to a display apparatus and aprojection display apparatus projector using these devices.

2. Description of Related Art

A polarizing illumination device capable of efficiently generating thesame type of polarized light beams is ideal as an illuminating devicefor use in a display apparatus, such as a liquid crystal apparatus,which employs a panel for modulating polarized light beams. Accordingly,an illuminating optical system has been proposed that converts randompolarized light beams emitted from a light source into the same type ofpolarized light beams and illuminates a liquid crystal apparatus withthe light beams so that a bright display is achieved. JapaneseUnexamined Patent Publication No. 7-294906 discloses an image displayapparatus equipped with such an illuminating optical system.

The principal part of the illuminating optical system disclosed inJapanese Unexamined Patent Publication No. 7-294906 will be brieflydescribed with reference to FIG. 15. This optical system mainlycomprises a lens plate 910, a plurality of polarizing beam splitters920, a plurality of reflecting prisms 930, and a plurality of λ/2phaseplates 940. Incident beams as randomly polarized beams are separatedinto two types of polarized beams (P polarized beams and S polarizedbeams) through the polarizing beam splitters 920 which are respectivelyprovided with polarizing separation planes 331 and the reflecting prisms930 which are respectively provided with reflecting planes 332. Afterthe separation, the polarization direction of polarized beams of one ofthe types is matched with that of polarized beams of the other type byusing the λ/2 phase plates 940, thereby obtaining polarized beams of thesame type and illuminating a liquid crystal device 950 with the lightbeams. In general, since a space for forming two types of polarizedbeams therein is needed in the polarized beam separation process, theoptical system is inevitably widened. Accordingly, this optical systemreduces the diameter of the beams, which are incident on the respectivepolarizing beam splitters 920, to less than about half the diameter ofsmall lenses 911 formed in the lens plate 910 by means of the smalllenses 911, and places the reflecting prisms (reflecting planes) 930 inthe spaces produced by the reduction of the diameter of the beams,whereby the same type of polarized beams are obtained without wideningthe optical system.

The optical system disclosed in Japanese Unexamined Patent PublicationNo. 7-294906 has, however, the following problems.

In reducing the diameter of the beam by the lens, generally, the minimumbeam diameter is almost directly and exclusively determined by therefractive power of the lens and parallelism of the light beam incidenton the lens. That is, in order to reduce the beam diameter to less thanhalf the lens diameter as in the optical system disclosed in JapaneseUnexamined Patent Publication No. 7-294906, it is necessary to use alens having an extremely high refractive power (in other words, a lenshaving an extremely small F-number) and a light source capable ofemitting a light beam having extremely high parallelism. However, a reallight source has a limited emission area. Therefore, parallelism of thelight beam emitted from the light source is not always good.

On the other hand, the polarizing separation ability of the polarizingseparation plane formed in the polarizing beam splitter is highlydependent on the incident angle of light. In other words, when the lightthat is incident on the polarizing separation plane has a large angularcomponent, the polarizing separation plane cannot exhibit and idealpolarizing separation ability, and S polarized beam mixes into the Ppolarized beam transmitting through the polarizing separation plane, andthe P polarized beam mixes into the S polarized beam reflected from thepolarizing separation plane. Consequently, it is impossible toexcessively increase the refractive power of the small lens used forreducing the diameter of the beam.

For the above reasons, it is difficult to sufficiently reduce thediameter of the light beam that is incident on the polarizing beamsplitter, and, in actuality, a relatively large amount of light alsodirectly enters the reflecting prism adjoining the polarizing beamsplitter. The light that is directly incident on the reflecting prism isreflected by the reflecting plane, enters the adjoining polarizing beamsplitter, and is separated into two types of polarized beams by thepolarizing separation plane in the same manner as the light beam that isdirectly incident on the polarizing beam splitter. The light beam thatis incident on the polarizing beam splitter through the reflecting prismand the light beam that is directly incident on the polarizing beamsplitter are different by 90° in the incident with respect to thepolarizing beam splitter. As a consequence of the existence of the lightbeam directly incident on the reflecting prism, the S polarized beamdirectly incident on the reflecting prism and separated through thepolarizing beam splitter mixes into the P polarized beam that transmitsthrough the polarizing beam splitter without changing its direction oftravel. Similarly, the S polarized beam mixes into the P polarized beamthat directly enters the polarizing beam splitter and is emitted throughthe reflecting prism and the λ/2 phase plate. Since the S polarized beammixed into the P polarized beam because of the existence of the lightbeam directly incident on the reflecting prism is quite unnecessary forthe liquid crystal device, it is absorbed by a polarizing plate andgenerates heat, which is the main factor that increases the temperatureof the polarizing plate.

Thus, in the process in which the conventional optical system disclosedin Japanese Unexamined Patent Publication No. 7-294906 converts randomlight beams emitted from the light source into polarized beams of thesame type, a relatively large number of polarized beams of another typeinevitably mix. As a result, the polarized beams, which are unnecessaryfor display and are polarized in a different direction, are required tobe absorbed by the polarizing plate in order to obtain an extremelybright display image. In addition, a large cooling device is essentialto restrict the increase in temperature of the polarizing plate causedby the absorption of the polarized beams.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to solve the aboveproblems by substantially restricting the mixing of other polarizedbeams, which are polarized in a different direction, in a process ofconverting randomly polarized beams emitted from a light source into thesame type of polarized beams.

In order to solve the above problems, a polarizing conversion device inaccordance with the present invention comprises a polarizing separationelement that has a polarizing separation plane for separating P and Spolarized beams by transmitting one of the polarized beams therethroughand reflecting the other polarized beam, and a reflecting plane disposedsubstantially parallel with the polarizing separation plane to reflectthe polarized beam reflected by the polarizing separation plane towardthe emergent direction of the polarized beam transmitted through thepolarizing separation plane, and a selective phase plate located on thelight emergent side of the polarizing separation element to align thepolarization direction of one of the S and P polarized beams separatedby the polarizing separation element with the polarization direction ofthe other polarized beam, wherein at least one of a shading means and anoptical attenuating means for preventing light from directly enteringthe reflective plane is provided on the light incident side of thepolarizing separation element.

The above structure enables the polarizing conversion device of thepresent invention to effectively prevent or restrict a phenomenon inwhich other polarized beams polarized in a different direction mix intopolarized beams of almost the same type polarized in the same direction.Therefore, it is possible to generate specific polarized beams with anextremely high efficiency.

In the above-mentioned polarizing conversion device, it is preferablethat the shading means or the optical attenuating means and thepolarizing separation element are integrated. It is therefore possibleto reduce light losses at an interface, and to thereby provide apolarizing conversion device having a high light use efficiency.

The shading means may be formed of a reflecting plate. When the shadingmeans is formed of a reflecting plate, it does not absorb much light,and therefore, does not generate much heat. Consequently, it is possibleto prevent peripheral optical elements from being thermally influencedby heat generation of the shading means. This is effective particularlywhen the selective phase plate is made of an organic substance that isnot heat-resistant.

Furthermore, when the shading means and the polarizing separationelement are integrated, the shading means may be formed of a reflectingfilm that is formed on the light incident surface of the polarizingseparation element. Such a structure also provides similar advantages asthose achieved in the situation wherein the shading means is formed of areflecting plate. The reflecting film may be formed of a dielectricmultilayer film, or a thin film of metal having high reflectivity, suchas silver or aluminum.

Still furthermore, the optical attenuating means in the polarizingconversion device may be formed of a light diffusing plate. When theoptical attenuating means is formed of a light diffusing plate, it ispossible to reduce the cost of the polarizing conversion device.

When the shading means and the polarizing separation element areintegrated, the optical attenuating means may be formed of a lightdiffusing surface formed on the light incident surface of the polarizingseparation element. Such a structure also provides similar advantages asthose achieved in the situation wherein the optical attenuating means isformed of a light diffusing plate. The light diffusing surface may beformed by roughening a specific region on the light incident surface ofthe polarizing separation element.

A polarizing illumination device in accordance with the presentinvention comprises a light source, a first optical element forseparating a light beam emitted from the light source into a pluralityof intermediate beams, and a second optical element disposed near theposition where the intermediate beams converge, wherein the secondoptical element has a condenser lens array that includes a plurality ofcondenser lenses for respectively condensing the intermediate beams, apolarizing separation element for spatially separating each of theintermediate beams into an S polarized beam and a P polarized beam, aselective phase plate for aligning the polarization direction of one ofthe S and P polarized beams separated by the polarizing separationelement with the polarization direction of the other polarized beam, anda superimposing lens for superimposing the polarized beams, thepolarizing separation element has a polarizing separation plane forseparating the P and S polarized beams by transmitting one of thepolarized beams therethrough and reflecting the other polarized beam anda reflecting plane disposed substantially parallel with the polarizingseparation plane to reflect the polarized beam reflected by thepolarizing separation plane toward the emergent direction of thepolarized beam transmitted through the polarizing separation plane, andat least one of a shading means and an optical attenuating means forpreventing each of the intermediate beams from directly entering thereflecting plane is interposed between the first optical element and thepolarizing separation element.

By adopting the above structure, the polarizing illumination device inaccordance with the present invention can effectively prevent orrestrict a phenomenon in which other polarized beams polarized in adifferent direction mix into polarized beams of almost the same typepolarized in the same direction. Therefore, it is possible to obtain asillumination light polarized beams with a considerably high degree ofpolarization.

According to the above structure, an incident beam is initiallyseparated into a plurality of intermediate beams and the intermediatebeams are finally superimposed on one illumination region. Therefore,even if the intensity distribution of the incident beam is veryimbalanced in the cross section thereof, it is possible to use asillumination light polarized beams that are uniform in brightness andcolor. Furthermore, even when each of the intermediate beams cannot beseparated into a P polarized beam and an S polarized beam that haveequal light intensity and spectral characteristics, and even when thelight intensity and the spectral characteristics of one of the polarizedbeams changes in a process of aligning the polarization directions ofthe polarized beams, it is possible to use as illumination lightpolarized beams that are uniform in brightness and color.

In addition, a plurality of polarized beam brought into almost one typeof polarization state are gathered as a whole, superimposed on oneillumination region, and form a large bundle of beams. Since thepolarized beams of this large bundle of beams themselves do notaccompany a beam component that has a large divergence angle,illumination with these light beams secures a high illuminationefficiency.

The light source may include a light source lamp and a reflector. Ametal halide lamp, a xenon lamp, a halogen lamp, and similar devices maybe used as the light source lamp, and a parabolic reflector, an ellipticreflector, a spherical reflector, and similar devices may be used as thereflector.

In the above polarizing illumination device, the shading means or theoptical attenuating means may be placed at any position between thepolarizing separation element and the first optical element. However, ifthe shading means or the optical attenuating means is integrated withthe polarizing separation element, it is possible to reduce light lossat the interface and to therapy provide a polarizing illumination devicehaving a high light use efficiency. Furthermore, the second opticalelement can be formed in one piece by integrating the shading means orthe optical attenuating means and the polarizing separation element, andin that situation, the second optical element can be made to beconsiderably compact.

The shading means or the optical attenuating means may be integratedwith the condenser lens array. This provides similar advantages to thoseof the situation in which the shading means or the optical attenuatingmeans is integrated with the polarizing element. Furthermore, in thissituation, when the condenser lens array integrated with the shadingmeans or the optical attenuating means is placed spatially apart fromother optical elements to form the second optical element (for example,the polarizing separation element and the selective phase plate), evenif the shading means or the optical attenuating means generates heat dueto light absorption, it is possible to prevent the other opticalelements from being thermally influenced by the heat generation.

In the above polarizing illumination device, the shading means may beformed of a reflecting plate. When the shading means is formed of areflecting plate, it does not absorb much light, and therefore, does notgenerate much heat. Consequently, it is possible to prevent peripheraloptical elements from being thermally influenced by heat generation ofthe shading means. This is effective particularly when the selectivephase plate is made of an organic substance that has small heatresistance. Moreover, when the shading means is formed of a reflectingplate, light reflected by the reflecting plate is allowed to return thelight source once, to be reflected again by the reflector at the lightsource, and to enter the polarizing separation element again. Therefore,it is possible to effectively use the light from the light sourcewithout waste.

Furthermore, when the shading means is integrated with the polarizingconversion device and the condenser lens array, the shading means may beformed of a reflecting film that is formed on the light incident surfaceof the polarizing separation element or the light emergent surface ofthe condenser lens array. Such a structure also provides similaradvantages to those of the situation in which the shading means isformed of a reflecting plate. The reflecting film may be formed of adielectric multilayer film, or a thin film of metal having highreflectivity, such as silver or aluminum.

In the above polarizing illumination device, the optical attenuatingmeans may be formed of a light diffusing plate. When the opticalattenuating means is formed of a light diffusing plate, it is possibleto achieve cost reduction of the polarizing illumination device.

When the optical attenuating means is integrated with the polarizingconversion device of the condenser lens array, it may be formed of alight diffusing surface formed on the light incident surface of thepolarizing separation element or the light emergent surface of thecondenser lens array. Such a structure also provides similar advantagesas those achieved in the situation in which the optical attenuatingmeans is formed of a light diffusing plate, and the situation in whichthe optical diffusing plate is integrated with the polarizing separationelement or the condenser lens array. The light diffusing surface may beformed by roughening a specific region on the light incident surface ofthe polarizing separation element or the light emergent surface of thecondenser lens array.

A display apparatus in accordance with the present invention comprises alight source, a first optical element for separating a light beamemitted from the light source into a plurality of intermediate beams, asecond optical element located near the position where the intermediatebeams converge, and a modulating device for modulating a light beamemitted from the second optical element, wherein the second opticalelement has a condenser lens array that includes a plurality ofcondenser lenses for respectively condensing the intermediate beams, apolarizing separation element for spatially separating each of theintermediate beams into an S polarized beam and a P polarized beam, aselective phase plate for aligning the polarization direction of one ofthe S and P polarized beams separated by the polarizing separationelement with the polarization direction of the other polarized beam, anda superimposing lens for superimposing the polarized beams, thepolarizing separation element has a polarizing separation plane forseparating the P and S polarized beams by transmitting the one of thepolarized beams therethrough and reflecting the other polarized beam anda reflecting plane disposed substantially parallel with the polarizingseparation plane to reflect the polarized beam reflected by thepolarizing separation plane toward the emergent direction of thepolarized beam transmitted through the polarizing separation plane, andat least one of a shading means and an optical attenuating means forpreventing each of the intermediate beams from directly entering thereflecting plane is interposed between the first optical element and thepolarizing separation element.

By adopting the above structure, the display apparatus in accordancewith the present invention can effectively prevent a phenomenon in whichother polarized beams polarized in a different direction mix intopolarized beams of almost the same type polarized in the same direction.Therefore, when a polarizing plate is used to obtain a requiredpolarized beam modulated by the modulating device, it is possible toprevent the increase in temperature of the polarizing plate caused byabsorption of an unnecessary polarized beam, and to substantiallysimplify and miniaturize a cooling device for cooling the polarizingplate. A liquid crystal device may be used as the modulating device.

According to the above structure, an incident beam is initiallyseparated into a plurality of intermediate beams and the intermediatebeams are finally superimposed on the modulating device. Therefore, evenif the light distribution of the light emitted from the light source isvery imbalanced in the cross section thereof, it is possible to obtainas illumination light polarized beams that are uniform in brightness andcolor. Consequently, it is possible to achieve a compact displayapparatus capable of producing a display that is bright and uniform inbrightness and color.

A projection display apparatus projector in accordance with the presentinvention comprises a light source, a first optical element forseparating a light beam emitted from the light source into a pluralityof intermediate beams, a second optical element disposed near theposition where the intermediate beams converge, a modulating device formodulating a light beam emitted from the second optical element, and aprojection optical system for projecting the light beam modulated by themodulating device onto a projection plane, wherein the second opticalelement has a condenser lens array that includes a plurality ofcondenser lenses for respectively condensing the intermediate beams, apolarizing separation element for spatially separating each of theintermediate beams into an S polarized beam and a P polarized beam, aselective phase plate for aligning the polarization direction of one ofthe S and P polarized beams separated by the polarizing separationelement with the polarization direction of the other polarized beam, anda superimposing lens for superimposing the polarized beams, thepolarizing separation element has a polarizing separation plane forseparating the P and S polarized beams by transmitting one of thepolarized beams therethrough and reflecting the other polarized beam anda reflecting plane located almost in parallel with the polarizingseparation plane to reflect the polarized beam reflected by thepolarizing separation plane toward the emergent direction of thepolarized beam transmitted through the polarizing separation plane, andat least one of a shading means and an optical attenuating means forpreventing each of the intermediate beams from directly entering thereflecting plane is interposed between the first optical element and thepolarizing separation element.

By adopting the above structure, the projection display apparatusprojector of the present invention can effectively prevent a phenomenonin which other polarized beams polarized in a different direction mixinto polarized beams of almost the same type polarized in the samedirection. Therefore, when a polarizing plate is used to obtain arequired polarized beam to be modulated by the modulating device, it ispossible to prevent the increase in temperature of the polarizing platecaused by absorption of an unnecessary polarized beam, and tosubstantially simplify and reduce the size of a cooling device forcooling the polarizing plate. A liquid crystal device may be used as themodulating device.

According to the above structure, an incident beam is initiallyseparated into a plurality of intermediate beams and the intermediatebeams are finally superimposed on the modulating device. Therefore, evenif the intensity distribution of the light emitted from the light sourceis very imbalanced in the cross section thereof, it is possible toobtain as illumination light polarized beams that are uniform inbrightness and color. Consequently, it is possible to achieve a compactdisplay apparatus capable of producing a display that is bright anduniform in brightness and color.

The projection display apparatus projector further comprises a colorlight separation means for separating the light beam emitted from thesecond optical element into a plurality of colored lights, a pluralityof modulating devices for respectively modulating the colored lights,and a colored light synthesizing means for synthesizing the coloredlights modulated by the modulating devices, wherein a synthesized beamsynthesized by the colored light synthesized means is projected onto theprojection plane through the projection optical system. Since exclusivemodulating devices can be placed respectively for more than twoseparated colored lights, it is possible to achieve a compact projectiondisplay apparatus projector capable of projecting and displaying a colorimage that is bright and has a high color reproducibility and a highresolution.

In the above projection display apparatus projector, the modulatingdevice may be formed of a reflection-type liquid crystal device. Ingeneral, the reflection-type liquid crystal device provides theadvantage of easily obtaining a relatively high aperture ratio even ifpixel density is increased. Therefore, adopting of the above structuremakes it possible to achieve a compact projection display apparatusprojector capable of projecting and displaying a color image that isbright and has a high color reproducibility and a high resolution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structure view of an optical system in apolarizing illumination device according to a first embodiment of thepresent invention.

FIG. 2 is a perspective view of a first optical element according to thefirst embodiment of the present invention.

FIG. 3 is a perspective view of a shading plate according to the firstembodiment of the present invention.

FIG. 4 is a perspective view of a polarizing separation unit arrayaccording to the first embodiment of the present invention.

FIG. 5 is a view showing the operation of a polarizing separation unitaccording to the first embodiment of the present invention.

FIG. 6 is a perspective view of a shading plate according to a firstmodification of the first embodiment of the present invention.

FIG. 7 is a perspective view of a shading plate according to a secondmodification of the first embodiment of the present invention.

FIG. 8 is a perspective view of a polarizing separation unit arrayaccording to a third modification of the first embodiment of the presentinvention.

FIG. 9 is a perspective view of a condenser lens array according to afourth modification of the first embodiment of the present invention.

FIG. 10 is a perspective view of a shading plate according to a fifthmodification of the first embodiment of the present invention.

FIG. 11 is a schematic structural view showing the principal part of anoptical system in a display apparatus according to a second embodimentof the present invention, in which the polarizing illumination deviceshown in FIG. 1 is incorporated.

FIG. 12 is a schematic structural view showing the principal part of anoptical system in a projection display apparatusprojector according to athird embodiment of the present invention, in which the polarizingillumination device shown in FIG. 1 is incorporated.

FIG. 13 is a schematic structural view showing the principal part of anoptical system in a projection display apparatusprojector according to afourth embodiment of the present invention, in which the polarizingillumination device shown in FIG. 1 is incorporated.

FIG. 14 is a schematic structural view showing the principal part of anoptical system in a modification of the projection displayapparatusprojector according to the fourth embodiment of the presentinvention, in which the polarizing illumination device shown in FIG. 1is incorporated.

FIG. 15 is a schematic structural view of a polarizing optical systemdisclosed in Japanese Unexamined Patent Publication No. 7-294906.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Modes for carrying out the present invention will be described below inconnection with embodiments and with reference to the drawings. In thefollowing embodiments, three directions orthogonal to one another are,for the sake of convenience, taken as an X direction (lateraldirection), a Y direction (longitudinal direction), and a Z direction,unless otherwise stated. Although S polarized beams are obtained as thesame type of polarized beams of the same type from randomly polarizedbeams in any of the embodiments, of course. P polarized beams may beobtained. Moreover, in the embodiments that will be described below,sections that have substantially the same functions and structure aredenoted by the same numerals, and a description thereof is omitted.

First Embodiment

FIG. 1 is a schematic structural plan view of the principal part of apolarizing illumination device according to a first embodiment. FIG. 1is a plan view in the XZ plane which passes through the center of afirst optical element 200 which will be described later. The polarizingillumination device 1 of this embodiment generally comprises a lightsource section 10 and a polarized light generation device 20 that arearranged along a system optical axis L. Light beams emitted from thelight source section 10 and polarized in random directions (hereinafterreferred to as randomly polarized beams) are converted by the polarizedlight generating device 20 into the same type of polarized beams thatare polarized in almost the same direction, and directed to anillumination region 90.

The light source section 10 generally comprises a light source lamp 101and a parabolic reflector 102. Light radiated from the light source lampis reflected by the parabolic reflector 102 in one direction, and madeincident on the polarized light generating device 20 in the form ofalmost parallel light beams. The light source section 10 is placed sothat a light source optical axis R thereof is shifted in parallel fromthe system optical axis L by a required distance D in the X direction.

The polarized light generating device 20 comprises a first opticalelement 200 and a second optical element 300.

The first optical element 200, as outwardly shown in FIG. 2, includes amatrix of a plurality of beam splitting lenses 201 each having arectangular outline in the XY plane. The positional relationship betweenthe light source section 10 and the first optical element 200 is set sothat the light source optical axis R aligns with the center of the firstoptical element 200. Light that is incident on the first optical element200 is split into a plurality of intermediate beams 202 by each beamsplitting lens 201, and simultaneously, the same number of condensedimages 203 as that of the beam splitting lenses are formed, by acondensing action of the beam splitting lenses, at positions in a plane(the XY plane in FIG. 1) perpendicular to the system optical axis L,where the intermediate beams coverage. The outline of each beamsplitting lens 201 in the XY plane is set so that it is similar to thatof the illumination region 90. Since it is assumed that the illuminationregion in this embodiment extends laterally in the X direction in the XYplane, the outline of the beam splitting lens 201 in the XY plane isalso extended laterally.

The second optical element 300 is a complex that generally includes acondenser lens array 310, a shading plate 370, a polarizing separationuntil array 320, a selective phase plate 380, and a superimposing lens390, and is placed in a plane (the XY plane in FIG. 1) perpendicular tothe system optical axis L near the positions where the condensed images203 are formed by the first optical element 200. When the light beamsthat are incident on the first optical element 200 are extremelyparallel, the condenser lens array 310 does not have to be included inthe second optical element. The second optical element 300 operates tospatially separate each intermediate beam 202 into a P polarized beamand an S polarized beam, aligns the polarization direction of onepolarized beam and that of the other polarized beam, and directs thebeams polarized in substantially the same direction to one point in theillumination region 90.

The condenser lens array 310 has almost the same structure as the firstoptical element 200, that is, it comprises a matrix of the same numberof condenser lenses 311 as that of the beam splitting lenses 201 of thefirst optical element 200. The condenser lens array 310 operates tocondense and direct each intermediate beam to a specific position in thepolarizing separation unit array 320. Therefore, it is preferable tooptimize the lens properties of the condenser lenses in accordance withthe properties of the intermediate beams 202 formed by the first opticalelement 200, and considering that the ideal placement of the principalray of the light incident on the polarizing separation unit array 320 isparallel with the system optical axis L. Generally, in consideration ofcost reduction and easy design of the optical system, an elemententirely identical with the first optical element 200 may be used as thecondenser lens array 310, or a condenser lens array that includescondenser lenses similar in shape to the beam splitting lenses 201 inthe XY plane may be used. Therefore, in this embodiment, the firstoptical element 200 is used as the condenser lens array 310. Thecondenser lens array 310 may be placed apart from the shading plate 370and the polarizing separation unit array 320 (on the side closer to thefirst optical element 200).

The shading plate 370, as outwardly shown in FIG. 3, includes an arrayof a plurality of shading surfaces 371 and a plurality of open surfaces372. The shading surfaces 371 and the open surfaces 372 are arranged ina manner corresponding to the arrangement of polarizing separation units330 which will be described later. Four broken lines parallel with the Xaxis on the shading plate 370 in FIG. 3 are drawn to explain thecorrespondence to the polarizing separation unit array which will bedescribed later. This also applies to a reflecting plate 373 shown inFIG. 6 and a light diffusing plate 376 shown in FIG. 7. Light beams thatare incident on the shading surfaces 371 of the shading plate 370 areblocked, and light beams that are incident on the open surfaces 372 passthrough the shading plate 370 unchanged. Therefore, the shading plate370 operates to control the light beams in accordance with the positionsthereon where the light beams transmit, and the shading surfaces 371 andthe open surfaces 372 are arranged so that the condensed images 203 arerespective formed by the first optical element 200 only on polarizingseparation planes 331 of the polarizing separation units 330 which willbe described later. A flat transparent member, such as a glass plate,partially provided with opaque films made of chrome, aluminum or similarmaterials as in this embodiment, an opaque flat plate, such as analuminum plate, provided with open sections, and similar structures maybe used as the shading plate 370. Particularly, when opaque films areused, even if they are directly formed on the condenser lens array 310or the polarizing separation unit array 320, which will be describedlater, it is possible to provide similar functions.

The polarizing separation unit array 320, as outwardly shown in FIG. 4,includes a matrix of a plurality of polarizing separation units 330. Thepolarizing separation units 330 are arranged corresponding to the lensproperties and arrangement of the beam splitting lenses 201 which formthe first optical element 200. Since the first optical element 200include the concentric beam splitting lenses 201 which all have the samelens properties and are arranged in a rectangular matrix in thisembodiment, the polarizing separation unit array 320 also includes allthe same polarizing separation units 320 which are arranged in the samedirection and in a crossed matrix. When the polarizing separation unitsaligned in the Y-direction column are of all the same type, it ispreferable that the polarizing separation unit array 320 includepolarizing separation units which are long in the Y direction and arearranged in the X direction, which is advantageous in reducing lightlosses at the interfaces between the polarizing separation units and inreducing the production cost of the polarizing separation unit array.

Each polarizing separation unit 330 is, as outwardly shown in FIG. 5, amember shaped like a quadrangular prism and provided with a polarizingseparation plane 331 and a reflecting plane 332 therein, and operates tospatially separate each intermediate light beam, that enters thepolarizing separation unit, into a P polarized beam and an S polarizedbeam. The outline of the polarizing separation unit 330 in the XY planeis similar to that of the beam splitting lens 201 in the XY plane, thatis, it is shaped like a rectangular which is extended laterally.Therefore, the polarizing separation plane 331 and the reflecting plane332 are placed so that they are arranged in the lateral direction (the Xdirection). The polarizing separation plane 331 and the reflecting plane332 are placed so that the polarizing separation plane 331 inclines atabout 45° with respect to the system optical axis L, the reflectingplane 332 is parallel to the polarizing separation plane 331. Theprojection area of the polarizing separation plane 331 in the XY plane(that is equal to the area of a P emergent surface 333 described later)and the projection area of the reflecting plane 332 in the XY plane(that is equal to the area of an S emergent surface 334 described later)are equal to each other. Therefore, in this embodiment, a width Wp of aregion in the XY plane, where the polarizing separation plane 331exists, and a width Wm of a region in the XY plane, where the reflectingplane 332 exists, are equally set so that they are each half a width Wof the polarizing separation unit in the XY plane. In general, thepolarization separation plane 331 may be made of a dielectric multilayerfilm, and the reflecting plane 332 may be made of a dielectricmultilayer film or an aluminum film.

Light incident on the polarizing separation unit 330 is separated by thepolarizing separation plane 331 into a P polarized beam 335 thattransmits through the polarizing separation plane 331 without changingits direction of travel and an S polarized beam 336 that is reflected bythe polarizing separation plane 331 and changes its direction of traveltoward the adjoining reflecting plane 332. The P polarized beam 335 isemitted from the polarizing separation unit through the P emergentsurface 33 unchanged, and the S polarized beam 336 again changes itsdirection of travel at the reflecting plane 332, and is emitted from thepolarizing separation unit through the S emergent surface 334substantially parallel with the P polarized beam 335. Therefore,randomly polarized beams incident on the polarizing separation unit 330are separated into two types of polarized beams polarized in differentdirections, the P polarized beam 335 and the S polarized beam 336, andare emitted substantially the same direction from different sections ofthe polarizing separation unit (the P emergent surface 333 and the Semergent surface 344). Since the polarizing separation unit has theabove-mentioned functions, it is necessary to lead each intermediatebeam 202 to the region of the polarizing separation unit 330 where thepolarizing separation plane 331 exists. Accordingly, the positionalrelationship between each polarizing separation unit 330 and eachcondenser lens 311 and the lens properties of the condenser lens 311 areset so that the intermediate beam enters the center of the polarizingseparation plane in the polarizing separation unit. Particularly, inthis embodiment, the condenser lens array 310 is placed offset from thepolarizing separation unit array 320 by the distance D, whichcorresponds to ¼ of the width W of the polarizing separation unit, inthe X direction so that the center axis of each condenser lens alignswith the center of the polarizing separation plane 331 in eachpolarizing separation unit 330.

Any polarizing separation unit array may be used as long as theabove-mentioned polarizing separation planes and reflecting planes areregularly formed therein, and it is not always necessary to use theabove-mentioned polarizing separation units as basic constituents.Herein, the polarizing separation units are discussed as constituentsonly to explain the function of the polarizing separation unit array.

Description will be made again with reference to FIG. 1.

The shading plate 370 is interposed between the polarizing separationunit array 320 and the condenser lens array 310 so that the center ofeach open surface 372 of the shading plate 370 is substantially alignedwith the center of the polarizing separation plane 331 of eachpolarizing separation unit 330. The opening width of the open surface372 (the opening width in the X direction) is set about half the width Wof the polarizing separation unit 330. As a result, since intermediatebeams are previously blocked by the shading surface 371 of the shadingplate 370, there are few beams that directly enter the reflecting plane332 without passing through the polarizing separation plane 331, andmost of the light beams passed through the open surface 372 of theshading plate 370 enter only the polarizing separation plane 331.Consequently, because of such placement of the shading plate 370, fewlight beams directly enter the reflecting planes 332 and enter theadjoining polarizing separation planes 331 through the reflecting planes332 in the polarizing separation unit.

The selective phase plate 380, in which λ/2 phase plates 381 areregularly arranged, is placed on the emergent side of the polarizingseparation unit array 320. That is, the λ/2 phase plates 381 arerespectively placed only at the P emergent surfaces 333 of thepolarizing separation units 330 which form the polarizing separationunit array 320, and no λ/2 phase plates 381 are placed at the S emergentsurfaces 334 (see FIG. 5). According to such an arrangement of the λ/2phase plates 381, when P polarized beams emitted from the polarizingseparation units 330 respectively pass through the λ/2 phase plates 381,they are conventional into S polarized beams by a polarization directionrotation action. On the other hand, since S polarized beams emitted fromthe S emitting surfaces 334 do not pass through the λ/2 phase plates381, they do not change their polarization direction and pass throughthe selective phase plate 380 unchanged. In summary, intermediate beamspolarized in random directions are converted into polarized beams of thesame type (in this case, the S polarized beams) by the polarizingseparation unit array 320 and the selective phase plate 380.

The superimposing lens 390 is placed on the emitting side of theselective phase plate 380. The light beams, which are converted into theS polarized beams by the selective phase plate 380, are directed to theillumination region 90 by the superimposing lens 390 and superimposed onthe illumination region. The superimposing lens 390 is not limited to asingle lens member, and it may be an assembly of a plurality of lenseslike the first optical element 200.

To summarize the operations of the second optical element 300, theintermediate beams 202 separated by the first optical element 200 (thatis, image planes cut out by the beam splitting lenses 201) aresuperimposed on the illumination area 90 by the second optical element300. At the same time, the intermediate beams, which are randomlypolarized beams, are spatially separated into two types of polarizedbeams polarized in different directions by the polarizing separationunit array 320 placed in the path, and converted into substantially onetype of polarized beams when they pass through the selective phase plate380. Since the shading plate 370 is placed on the incident side of thepolarizing separation unit array 320 and the intermediate beams arethereby allowed to enter only the polarizing separation planes 331 inthe polarizing separation units 330, few intermediate beams enter thepolarizing separation planes 331 through the reflecting planes 332, andtherefore, the polarized beams emitted from the polarizing separationunit array 320 are limited to substantially one type. Consequently, theillumination region 90 is illuminated substantially uniformly withsubstantially one type of polarized beams.

As described above, the polarizing illumination device 1 of thisembodiment is advantageous in that randomly polarized beams emitted fromthe light source section 10 are converted into substantially one type ofpolarized beams by the polarized light generating device 20 thatincludes the first optical element 200 and the second optical element300, and the illumination region 90 can be illuminated uniformly withthe light beams polarized in the same direction. Moreover, since theprocess of generating the polarized beams accompanies little loss oflight, almost all the light emitted from the light source section can bedirected to the illumination region 90, which provides extremely highlight use efficiency. Furthermore, since the shading plate 370 is placedin the second optical element 300, other beams polarized in a differentdirection rarely mix into polarized beams of the same type forilluminating the illumination region 90. Therefore, when the polarizingillumination device of the present invention is used as a device forilluminating a modulating device that produces a display using polarizedbeams such as a liquid crystal device, it is possible to obviate apolarizing plate which is conventionally placed on the side of themodulating device where the illumination light enters. Even if thepolarizing plate is placed as is conventionally done, since the amountof light absorbed by the polarizing plate is extremely small, it ispossible to substantially reduce the size of a cooling device that isneeded to minimize heat generation of the polarizing plate and themodulation device. As mentioned above, the size of the condensed images203 formed by the first optical element 200 is influenced by theparallelism of light beams that enter the first optical element (lightbeams emitted from the light source in the illumination device). Whenparallelism is low, since only a large condensed image can be formed, alarge number of intermediate beams directly enter the reflecting planeswithout passing the polarizing separation planes in the polarizingseparation units, and therefore, a phenomenon in which other beamspolarized in a different direction mix into the illumination beams isinevitable. Accordingly, the structure of the polarizing illuminationdevice of the present invention has a great effect, particularly inadopting a light source for emitting light beams having low parallelismin the apparatus.

In this embodiment, the condenser lens array 310, the shading plate 370,the polarizing separation unit array 320, the selective phase plate 380,and the emergent-side lens 390, which form the second optical element300, are optically integrated, so that light losses caused at interfacestherebetween are reduced, and the light use efficiency is furtherenhanced. Although it is not always necessary to optically integratethese optical elements, it is preferable to optically integrate or fixthe shading plate 370 on the light incident surface of the polarizingseparation unit array 320 in order to effectively prevent other beamspolarized in a different direction from mixing into the illuminationlight. As a method of optically integrating the shading plate 370 withthe light incident surface of the polarizing separation unit array 320,it is possible to stick the shading plate 370 to the light incidentsurface of the polarizing separation unit array 320 with an adhesivelayer, or to directly form the shading surfaces 371 on the lightincident surface of the polarizing separation unit array 320 as will bedescribed later. On the other hand, as a method of fixing the shadingplate 370 on the light incident surface of the polarizing separationunit array 320, it is possible to stick the peripheral portion of theshading plate 370 on the peripheral portion of the light incidentsurface of the polarizing separation unit array 320 by using adouble-sided tape or similar device. In this situation, it is necessaryto stick the entire peripheral portion of the shading plate 370, and theperipheral portion only has to be stuck at at least two points. In orderto fix the shading plate 370 parallel with the light incident surface ofthe polarizing separation unit array 320, it is preferable to set thesticking points so that they are almost symmetrical with respect to thecenter point of the shading plate 370.

Furthermore, the beam splitting lenses 201 which form the first opticalelement 200 each extend laterally in accordance with the shape of theillumination region 90 like a laterally extended rectangle, and at thesame time, two types of polarized beams emitted from the polarizingseparation unit array 320 are separated in the lateral direction (the Xdirection). This makes it possible to enhance illumination efficiency(light use efficiency) without wasting the light even in illuminatingthe illumination region 90 which is shaped like a laterally extendedrectangle.

In general, when light beams polarized in random directions are merelyseparated into P polarized beams and S polarized beams, the overallwidth of the separated beams doubles, which increases the size of theoptical system. The polarizing illumination device of the presentinvention, however, forms a plurality of minute condensed images 203through the first optical element 200, effectively uses the spacesprovided in the formation process where no light exists, andrespectively places the reflecting planes 332 of the polarizationseparation units 330 in the spaces, thereby absorbing the lateralwidening of the beams caused by the separation into two types ofpolarized beams. As a result, the overall width of the beams does notincrease, and a compact optical system can be achieved.

First Modification of First Embodiment

In the first embodiment, the shading surfaces 371 that form the shadingplate 370 may be replaced with reflecting planes for reflecting light inalmost the opposite direction. That is, a reflecting plate 373 thatincludes a plurality of reflecting surfaces 374 and a plurality of opensurfaces 375, as shown in FIG. 6, may be adopted instead of the shadingplate 370 in the first embodiment. The reflecting surfaces 374 each caneasily be formed of a dielectric multilayer film, a thin film made ametal having high reflectivity, such as silver or aluminum, or acombination thereof, and an extremely high reflectivity of more thanninety percent can be obtained depending on the type of the film. Evenif the reflecting surfaces 374 are directly formed on the condenser lensarray 310 or the polarizing separation unit array 320 shown in FIG. 1,similar functions are provided.

As opposed to the shading surfaces 371, the reflecting surfaces 374hardly absorb light. Therefore, the adoption of the reflecting plate 373can prevent peripheral optical elements from being thermally influencedby heat generation thereof. In addition, the light reflected by thereflecting surfaces 374 and reflected by the parabolic reflector 102placed in the light source section 10, can make enter again into thepolarized light generating device 20 and lead into the open sections 375of the reflecting plate 373. Then it is possible to efficiently use thelight from the light source without waste.

Second Modification of First Embodiment

In the first embodiment, even if the shading surfaces for forming theshading plate are replaced with light diffusing surfaces for diffusinglight, almost the same advantages as those obtained by the shadingsurfaces can be provided. That is, in the first embodiment, a lightdiffusing plate 376 that includes an arrangement of a plurality of lightdiffusing surfaces 377 and a plurality of open surfaces 378, as shown inFIG. 7, may be adopted instead of the shading plate 370. Since lightincident on the light diffusing surface 377 is diffused, it is possibleto substantially reduce the intensity of light that directly enters thereflecting plane without passing through the polarizing separation planeof the polarizing separation unit, and to effectively prevent aphenomenon in which other beams polarized in a different direction mixinto illuminating beams including substantially the same type ofpolarized beams that are polarized in the same direction. Each lightdiffusing surface 377 can easily be realized by forming a lightdiffusing member on or inside a flat transparent substrate, making thesurface of the transparent substrate uneven, or merely roughening thesurface thereof. Even if the light diffusing surfaces 377 are directlyformed on the condenser lens array 310 or the polarizing separation unitarray 320 shown in FIG. 1, similar functions can be provided.

Adopting the light diffusing plate 376 makes it possible to reduce thecost compared with adopting the shading plate 370 and the reflectingplate 373 using dielectric multilayer films, metal thin films, orsimilar materials.

Third Modification of First Embodiment

Although the shading plate 370, the reflecting plate 373 and the lightdiffusing plate 376 in the first embodiment and the above-mentionedfirst and second modifications are each an optical element that isphysically independent from the condenser lens array 310 and thepolarizing separation unit array 320 located in front and in the rearthereof, even if the shading surface 371 for forming the shading plate370, the reflecting surfaces 374 for forming the reflecting plate 373,or the light diffusing surfaces 377 for forming the light diffusingplate 376 are directly formed on the light incident surfaces of thepolarizing separation units 330 for forming the polarizing separationunit array 320, the same advantages as those obtained in the use ofthese optical elements can be obtained.

This modification will be specifically described with reference to FIG.8. In a polarizing separation unit array 320A whose outward appearanceis shown in FIG. 8, shading surfaces 321 are directly formed on lightincident surfaces of polarizing separation units 330A which form thepolarizing separation unit array 320A, and regions 322 where no shadingsurfaces are formed correspond to the open surfaces 372 of theabove-mentioned shading plate 370 for transmitting light therethrough.When the polarizing separation unit array 320A having the shadingsurfaces 321 directly formed thereon is used as in this modification,since there is no need to use the shading plate 370 as a physicallyindependent optical element, it is possible to reduce the size and costof the second optical element. Of course, reflecting surfaces of lightdiffusing surfaces may be directly formed on the polarizing separationunits 330A instead of the shading surfaces 321, and this situationprovides the same advantages as those of this modification.

Fourth Modification of First Embodiment

Although the shading plate 370, the reflecting plate 373 and the lightdiffusing plate 376 in the first embodiment and the above-mentionedfirst and second modifications are each an optical element that isphysically independent from the condenser lens array 310 and thepolarizing separation unit array 320 located in front and in the rearthereof, even if the shading surfaces 371 for forming the shading plate370, the reflecting surfaces 373 for forming the reflecting plate 373,or the light diffusing surfaces 374 for forming the light diffusingplate 376 are directly formed on the condenser lenses 311 for formingthe condenser lens array 310, the same advantages as those in the use ofthese optical elements can be obtained.

This modification will be specifically described with reference to FIG.9. In a condenser lens array 310A whose outward appearance is shown inFIG. 9, shading surfaces 312 are directly formed on surfaces ofcondenser lenses 311A for forming the condenser lens array 310A fromwhich light is emitted, and regions 313 where no shading surfaces areformed correspond to the open surfaces 372 of the above-mentionedshading plate 370 for transmitting light therethrough. When thecondenser lens array 310A having the shading surfaces 312 directlyformed thereon is used as in this modification, since there is no needto use the shading plate 370 as a physically independent opticalelement, it is possible to reduce the size and cost of the secondoptical element. Of course, reflecting surfaces or light diffusingsurfaces may be directly formed on the condenser lenses 311A instead ofthe shading surfaces 312 of this modification, and this case providesthe same advantages as those of this modification. In this modification,if the condenser lens array 310A is placed spatially apart from thepolarizing separation unit array and the selective phase plate that areother optical elements for forming the second optical element, it ispossible to prevent the optical elements from being influenced by heatgeneration resulting from light absorption by the shading surfaces, thereflecting surfaces, and the light diffusing surfaces.

Fifth Modification of First Embodiment

Although a flat transparent member like a glass plate is partiallyprovided with opaque films made of chrome, aluminum, or similar materialin the shading plate 370 of the first embodiment, an opaque flat platesuch as an aluminum plate may be provided with open sections.

This modification will be specifically described with reference to FIG.10. In a shading plate 370A whose outward appearance is shown in FIG.10, an opaque flat plate 371A is provided with open sections 372A. Whenthe shading plate 370A is fixed on the light incident surface of thepolarizing separation unit array 320 in order to effectively preventother beams polarized in a different direction from mixing into theillumination light, two sticking points 379a and 379b on the peripheralsection of the shading plate 371A are fixed on the light incidentsurface of the polarizing separation unit array 230 with double-sidedtapes. Since the sticking points 379a and 379b are positioned so thatthey are almost symmetrical with respective to the center point of theshading plate 370A, the shading plate 370A is allowed to be fixed inparallel with the light incident surface of the polarizing separationunit array 320.

When the shading plate 370A having the opaque flat plate 371A, such asan aluminum plate, provided with the open sections 372A is used as inthis modification, it is possible to reduce the costs compared with theshading plate 370 in which a flat transparent member, such as a glassplate, is partially provided with opaque films made of chrome, aluminum,or similar material.

Second Embodiment

A description will be given of a direct-view display apparatus in whichthe polarizing illumination device 1 of the first embodiment isincorporated. In this embodiment, a transmission-type liquid crystaldevice is used as a modulating device for modulating light beams emittedfrom the polarizing illumination device according to displayinformation.

FIG. 11 is a schematic structural view showing the principal part of anoptical system of a display apparatus 2 according to this embodiment,and shows the sectional structure in the XZ plane. The display apparatus2 of this embodiment roughly comprises the polarizing illuminationdevice 1 shown described in the first embodiment, a reflecting mirror510, and a liquid crystal device 520.

The polarizing illumination device 1 has a light source section 10 foremitting randomly polarized beams in one direction, and the randomlypolarized beams emitted from the light source section 10 are convertedinto substantially the same type of polarized beams by a polarized lightgenerating device 20. The reflecting mirror 510 turns the lighttraveling direction of the polarized beams emitted from the polarizingillumination device 1 by about 90°. The liquid crystal device 520 isilluminated with substantially the same type of polarized beams.Polarizing plates 521 are placed in front of and behind the liquidcrystal device 520. A light diffusing plate (not shown) maybe placedbefore the liquid crystal device 520 (on the side of the reflectingmirror 510) for the purpose of improving the angle of view.

The display apparatus 2 having such a structure employs a liquid crystaldevice for modulating the same type of polarized beams. Therefore, ifrandomly polarized beams are directed to the liquid crystal device byusing a conventional illumination device, about half the randomlypolarized beams are absorbed by the polarizing plates 521 and turnedinto heat, whereby the light use efficiency is low. The displayapparatus 2 of this embodiment, however, substantially improves such aproblem.

In the polarizing illumination device 1 of the display apparatus 2according to this embodiment, only one type of polarized beams, forexample, P polarized beams, are subjected to a rotary polarizationaction by the λ/2 phase plate, and the polarization direction thereof ismade identical with that of the other type of polarized beams, forexample, S polarized beams. Since substantially the same type ofpolarized beams, which are polarized in the same direction, are directedto the liquid crystal device 520, the amount of light to be absorbed bythe polarizing plates 521 is extremely small, which makes it possible toenhance the use efficiency of the source light, and to thereby obtain abright display state.

Particularly, in the polarizing illumination device 1 used as anillumination device, since the shading plate 370 is placed inside thesecond optical element 300, other polarized beams which are unnecessaryfor display on the liquid crystal device rarely mix into theillumination light emitted from the polarizing illumination device 1. Asa result, the amount of light absorbed by the polarizing plate 521placed on the light incident side of the liquid crystals device 520 isextremely small, and therefore, the amount of heat generated in lightabsorption is extremely small. Consequently, it is possible to omit acooling device for minimizing the increase in temperature of thepolarizing plate 521 and the liquid crystal device 520, or tosubstantially reduce the size of the cooling device even if suchomission is impossible.

Third Embodiment

A description will be given of a first example of a projection displayapparatus projector in which the polarization illumination device 1described in the first embodiment is incorporated. In this embodiment, atransmission-type liquid crystal device is used as a modulating devicefor modulating light beams emitted from the polarizing illuminationdevice according to display information.

FIG. 12 is a schematic structural view showing the principal part of anoptical system of a projection display apparatusprojector 3 according tothis embodiment, and shows the sectional structure in the XZ plane. Theprojection display apparatusprojector 3 of this embodiment generallycomprises the polarizing illumination device 1 described in the firstembodiment, a colored light separating means for separating a whitelight beam into three colored lights, three transmission-type liquidcrystal devices for modulating the colored lights according to displayinformation and thereby forming display images, a colored lightsynthesizing means for forming a color image by synthesizing the threecolored lights, and a projection optical system for projecting anddisplaying the color image.

The polarizing illumination device 1 of this embodiment has a lightsource section 10 for emitting randomly polarized beams in onedirection, and the randomly polarized beams emitted from the lightsource section 10 are converted into substantially the same type ofpolarized beams by a polarized light generating device 20.

First, the red light of the light emitted from the polarizingillumination device 1 transmits through a blue-green reflecting dichroicmirror 401 serving as the colored light separating means, and the bluelight and the green light are reflected. The red light is reflected by areflecting mirror 403 and reaches a liquid crystal device 411 for redlight. On the other hand, the green light of the blue and green lightsis reflected by a green reflecting dichroic mirror 402 that also servesas the colored light separating means, and reaches a liquid crystaldevice 412 for green light.

Since the blue light has the longest optical path of the colored lights,a light guide means 430 formed of a relay lens system comprising anincident lens 431, a relay lens 432, and an emergent lens 433 isprovided for the blue light. That is, after transmitting through thegreen reflecting dichroic mirror 402 and the incident lens 431, the bluelight is first reflected by a reflecting mirror 435, and directed to andfocused onto the relay lens 432. After being focused onto the relaylens, the blue light is directed to the emergent lens 433 by areflecting mirror 436, and then, reaches a liquid crystal device 413 forblue light. The liquid crystal devices 411, 412, and 413 located atthree positions respectively modulate the colored lights so that thecolored lights contain corresponding image information, and make themodulated colored lights enter a crossed dichroic prism 450 serving asthe colored light synthesizing means. The crossed dichroic prism 450includes a dielectric multilayer film for reflecting red light and adielectric multilayer film for reflecting blue light which are crossedin the form of X, and synthesizing the modulated light beams, therebyforming a color image. The color image formed therein is enlarged andprojected onto a screen 470 by a projection lens 460 serving as theprojection optical system, so that a projection image is formed.

The projection display apparatus projector 3 having such a structureemploys the liquid crystal devices each for modulating one type ofpolarized beam. Therefore, if randomly polarized beams are directed tothe liquid crystal device by using a conventional illumination device,about half of them are absorbed by a polarizing plate (not shown) andturned into heat. Therefore, the light use efficiency is low, and thereis a need for a large and noisy cooling device for minimizing heatgeneration of the polarizing plate. The projection display apparatusprojector 3 of this embodiment, however, substantially improves suchproblems.

In the polarizing illumination device 1 of the projection displayapparatus projector 3 according to this embodiment, only one type ofpolarized beam, for example, a P polarized beam is subjected to therotary polarization action by a λ/2 phase plate, and the polarizationdirection thereof is made identical with that of the other type ofpolarized beam, for example, and S polarized beam. Since substantiallythe same type of polarized beams, which are polarized in the samedirection, are directed to the liquid crystal devices 411, 412, and 413located at three position, the amount of light to be absorbed by thepolarizing plate is extremely small, which makes it possible to enhancethe light use efficiency, and to thereby obtain a bright projectionimage.

Particularly, in the polarizing illumination device 1 used as anillumination device, since the shading plate 370 is placed inside thesecond optical element 300, other polarized beams which are unnecessaryfor display on the liquid crystal device rarely mix into theillumination light emitted from the polarizing illumination device 1. Asa result, the amount of light absorbed by polarizing plates (not shown)respectively placed on the light incident sides of the liquid crystaldevices 411, 412, and 413 located at three positions is extremely small,and therefore, the amount of heat generated in light absorption isextremely small. Consequently, it is possible to substantially reducethe size of a cooling device for minimizing the increase in temperatureof the polarizing plates and the liquid crystal devices. As mentionedabove, a small cooling device will do for a projection display apparatusprojector capable of displaying a considerably bright projection imagewith a considerably high-power light source lamp, which makes itpossible to reduce noise of the cooling device, and to thereby achieve aquiet and high-performance projection display apparatus projector.

Furthermore, the polarizing illumination device 1 spatially separatestwo types of polarized beams in the lateral direction (the X direction)by the second optical element 300. Therefore, the polarizingillumination device 1 does not waste the light, and is convenient forilluminating a liquid crystal device shaped like a laterally extendedrectangle.

As described in connection with the above described first embodiment,the widening of light beams emitted from the polarizing separation unitarray 320 is restricted although the polarizing illumination device 1 ofthis embodiment incorporates polarizing conversion optical elementstherein. This means that minimal light enters the liquid crystal deviceat a large angle in illuminating the liquid crystal device. Accordingly,it is possible to achieve a bright projection image without using aprojection lens system having a small F-number and an extremely largeaperture, and to thereby achieve a compact projection display apparatusprojector.

Since the crossed dichroic prism 450 is used as the colored lightsynthesizing means in this embodiment, it is possible to reduce the sizeof the apparatus. Furthermore, since the optical paths between theliquid crystal devices 411, 412, and 413, and the projection lens systemare short, even if the projection lens system has a relatively smallaperture, it is possible to achieve a bright projection image. Stillfurthermore, though only one of the three optical paths of the coloredlights is difficult in length from the others, since the light guidemeans 430 formed of a relay lens system comprising the incident lens431, the relay lens 432, and the emergent lens 433 is provided for theblue light having the longest optical path, no color inconsistencyarises.

The projection display apparatus projector may comprise a mirror opticalsystem using two dichroic mirrors as the colored light synthesizingmeans. Of course, it is also possible in that case to incorporate thepolarizing illumination device of this embodiment, and to form ahigh-quality bright projection image having a high light use efficiency,similarly to this embodiment.

Fourth Embodiment

Another embodiment of a projection display apparatus projector in whichthe polarizing illumination device 1 described in the first embodimentis incorporated will be described. In this embodiment, reflection-typeliquid crystal devices are used as modulating devices for modulatinglight beams emitted from the polarizing illumination device according todisplay information.

FIG. 13 is a schematic structural plan view of the principal part of anoptical system in a projection display apparatusprojector 4 of thisembodiment. The projection display apparatusprojector 4 of thisembodiment generally comprises the polarizing illumination device 1 ofthe first embodiment, a polarizing beam splitter 480, a crossed dichroicprism 450 doubling as the colored light separation means and the coloredlight synthesizing means, three reflection-type liquid crystal devices414, 415, and 416 serving as modulating devices, and a projection lens460 serving as the projection optical system.

The polarizing illumination device 1 has a light source section 10 foremitting randomly polarized beams in one direction, and the randomlypolarized beams emitted from the light source section 10 are convertedinto substantially the same type of polarized beams (S polarized beamsin this embodiment) by a polarized light generating device 20.

The light beams emitted from the polarizing illumination device 1 enterinto the polarizing beam splitter 480, and are reflected by a polarizingseparation plane 418. Then, the traveling direction of the light beamsis changed by approximately 90°. Then, the light beams enter theadjoining crossed dichroic prism 450. Although most of the light beamsemitted from the polarizing illumination device 1 are S polarized beams,a few polarized beams polarized in a different direction from the Spolarized beams (P polarized beams in this embodiment) sometimes mix,and the light beams polarized in the different direction (the Ppolarized beams) transmit through the polarizing separation plane 481unchanged, and are emitted from the polarizing beam splitter 480 (theseP polarized beams do not serve as illumination light for illuminatingthe liquid crystal devices.)

The S polarized beams that are incident on the crossed dichroic prism450 are separated into three light beams of red, green, and blue by thecrossed dichroic prism 450 in accordance with the wavelength, and thelight beams respectively reach the reflection liquid crystal device 414for red light, the reflection liquid crystal device 415 for green light,and the reflection liquid crystal device 416 for blue light, therebyilluminating the liquid crystal devices. That is, the crossed dichroicprism 450 acts as the colored light separation means for illuminationlight for illuminating the liquid crystal devices.

The liquid crystal devices 414, 415, and 416 used in this embodiment areof the reflection-type. They modulate respective colored lights, andprovide the colored lights with corresponding external displayinformation. At the same time, they respectively change the polarizationdirections of the light beams emitted from the liquid crystal devices,and almost reverse the direction of travel of the light beams.Therefore, the light beams respectively reflected from the liquidcrystal devices are partially brought to a P polarized state accordingto display information, and then emitted. The modulated light beamsemitted from the liquid crystal devices 414, 415, and 416 (mainly Ppolarized beams) enter the crossed dichroic prism 450 again, aresynthesized into one optical image, and enter the adjoining polarizingbeam splitter 480 again. That is, the crossed dichroic prism 450 acts asthe colored light synthesizing means for the modulated light beamsemitted from the liquid crystal devices.

Since the light beams modulated by the liquid crystal devices 414, 415,and 416 of the light beams that are incident on the polarizing beamsplitter 480 are P polarized beams, they transmit through the polarizingseparation plane 481 of the polarizing beam splitter 480 unchanged, andform an image on a screen 470 through the projection lens 460.

The projection display apparatus projector 4 having such a structurealso employs liquid crystal devices that each modulate one type ofpolarized beam, similarly to the above described projection displayapparatus projector 3. Therefore, when a conventional illuminationdevice for using randomly polarized beams as illumination light isemployed, light beams separated by the polarizing beam splitter 480 anddirected to the reflection-type liquid crystal devices are reduced toapproximately half the number of the randomly polarized beams, the lightuse efficiency is low and a bright projection image is difficult toobtain. In the projection display apparatus projector 4 of thisembodiment, however, such a problem is substantially improved.

That is, the projection display apparatus projector 4 of this embodimentcan efficiently generate substantially the same type of polarized beams,they are polarized in the same direction, by using the polarizingillumination device 1 of the present invention instead of theconventional illumination device, and therefore, almost all light beamsthat are incident on the polarizing beam splitter 480 are directed asillumination light beams to the reflection-type liquid crystal devices414, 415, and 416 located at three positions. As a result, it ispossible to obtain a bright projection image that is uniform inbrightness and color.

Particularly, in the polarizing illumination device 1 used as anillumination device, since the shading plate 370 is placed inside thesecond optical element 300, other polarized beams that are unnecessaryfor display on the liquid crystal apparatus hardly mix into theillumination light emitted from the polarizing illumination device 1.Therefore, it is possible to obtain high-quality illumination lightbeams polarized in the same direction, and to thereby succeed inobtaining a high-quality bright projection image.

Moreover, the second optical element 300 in the polarizing illuminationdevice 1 spatially separates two types of polarized beams in the lateraldirection (the X direction). Therefore, the polarizing illuminationdevice 1 does not waste the light and is convenient for illuminating aliquid crystal device shaped like a laterally extended rectangle.

As described in connection with the above described first embodiment,the widening of light beams emitted from the polarizing separation unitarray 320 is restricted although the polarizing illumination device 1 ofthis embodiment incorporates polarizing conversion optical elementstherein. This means that minimal light enters the liquid crystal deviceat a large angle in illuminating the liquid crystal device. Accordingly,it is possible to achieve a bright projection image without using aprojection lens system having a small F-number and an extremely largeaperture, and to thereby achieve a compact projection display apparatusprojector .

Condenser lenses 417 may be respectively interposed between the crosseddichroic prism 450 and the liquid crystal devices 414, 415, and 416located at three positions in the projection display apparatus projector4 of this embodiment. FIG. 14 shows a schematic structure of an opticalsystem in that situation. Since such placement of these condenser lensesallows illumination light beams from the polarizing illumination device1 to be directed to the liquid crystal devices while restricting thewidening of the light beams, it is possible to further improve theefficiency in illuminating the liquid crystal devices, and the incidentefficiency in making light beams reflected by the liquid crystal devicesenter the projection lens 460. From the viewpoint of reduction of lightlosses at the lens interfaces, it is preferable to place each condenserlens integrally with the liquid crystal device as shown in FIG. 14, orwith the crossed dichroic prism.

Although S polarized beams are used as illumination light in theprojection display apparatus projector 4 of this embodiment. P polarizedbeams may be used as illumination light. In this case, the polarizingillumination device 1 and the crossed dichroic prism 450 are placedopposed to each other through the polarizing beam splitter 480.

Furthermore, though the crossed dichroic prism is used as the coloredlight separation means and the colored light synthesizing means in theembodiment, the projection display apparatus projector may comprise twodichroic mirrors instead. Of course, it is also possible in that case toincorporate the polarizing illumination device of this embodiment, andto form a high-quality bright projection image having a high light useefficiency, similarly to this embodiment.

As described above, according to the present invention, it is possibleto achieve a polarizing conversion device and a polarizing illuminationdevice capable of generating with high efficiency only the same type ofpolarized beams that have a more uniform light intensity distribution ina illumination region than incident light beams, and, at the same, thatare polarized in the same direction. Furthermore, it is possible toeasily achieve a display apparatus and a projection display apparatusprojector capable of displaying a high-quality bright image through theuse of the polarizing conversion device and the polarizing illuminationdevice of the present invention.

1. A polarizing conversion device, comprising: a polarizing separationelement having a light incident side, a light emergent side, apolarizing separation plane that separate P and S polarized beams bytransmitting one of the P and S polarized beams therethrough toward thelight emergent side of the polarizing separation element and reflectingthe other of the P and S polarized beams, and a reflecting planedisposed substantially parallel with said polarizing separation planethat reflects the other of the P and S polarized beams reflected by saidpolarizing separation plane toward the light emergent side of thepolarizing separation element; a selective phase plate disposed at thelight emergent side of said polarizing separation element that aligns apolarization direction of one of the P and S polarized beams separatedby said polarizing separation element with a polarization direction ofthe other of the P and S polarized beams, and a device for preventinglight from directly entering said reflecting plane disposed at the lightincident side of said polarizing separation element.
 2. The polarizingconversion device according to claim 1, wherein the device forpreventing light from directly entering said reflective plane includesat least one of a shading device and an optical attenuating device. 3.The polarizing conversion device according to claim 2, wherein saidshading device is a reflecting plate.
 4. The polarizing conversiondevice according to claim 2, wherein said shading device is a reflectingfilm, and said reflecting film is formed on a light incident surface ofthe light incident side of said polarizing separation element.
 5. Thepolarizing conversion device according to claim 2, wherein said opticalattenuating device is a light diffusing plate.
 6. The polarizingconversion device according to claim 2, wherein said optical attenuatingdevice is a light diffusing surface formed on a light incident surfaceof the light incident side of said polarizing separation element.
 7. Thepolarizing conversion device according to claim 1, wherein said devicefor preventing light from directly entering said reflecting plane andsaid polarizing separation element are integrated with each other.
 8. Apolarizing illumination device, comprising: a light source that emits alight beam; a first optical element that separates the light beamemitted from said light source into a plurality of intermediate beamsthat converge at a converging position; and a second optical elementdisposed at or near the converging position, the second optical elementincluding: a condenser lens array that includes a plurality of condenserlenses that respectively condense the intermediate beams; a polarizingseparation element that spatially separates each of the intermediatebeams into an S polarized beam and a P polarized beam, the polarizingseparation element including a light incident side, a light emergentside, a polarizing separation plane that separates P and S polarizedbeams by transmitting one of the P and S polarized beams therethroughtoward the light emergent side of the polarizing separation element andreflecting the other of the P and S polarized beams, and a reflectingplane disposed substantially parallel with said polarizing separationplane that reflects the other of the P and S polarized beams reflectedby said polarizing separation plane toward the light emergent side ofthe polarizing separation element; a selective phase plate that aligns apolarization direction of one of the P and S polarized beams isseparated by said polarizing separation element with a polarizationdirection of the other of the P and S polarized beams; a superimposinglens that superimposes the polarized beams; and a device for preventingeach of the intermediate beams from directly entering said reflectingplane interposed between said first optical element and said polarizingseparation element.
 9. The polarizing illumination device according toclaim 8, wherein the device for preventing each of the intermediatebeams from directly entering said reflecting plane includes at least oneof a shading device and an optical attenuating device.
 10. Thepolarizing illumination device according to claim 9, wherein saidshading device is a reflecting plate.
 11. The polarizing illuminationdevice according to claim 9, wherein said shading device is a reflectingfilm and said reflecting film is formed on a light incident surface ofthe light incident side of said polarizing separation element.
 12. Thepolarizing illumination device according to claim 9 47, wherein saidshading device is a reflecting film and said reflecting film is formedon a light emergent surface of said condenser lens array.
 13. Thepolarizing illumination device according to claim 9, wherein saidoptical attenuating device is a light diffusing plate.
 14. Thepolarizing illumination device according to claim 9, wherein saidoptical attenuating device is a light diffusing surface formed on alight incident surface of the light incident side of said polarizingseparation element.
 15. The polarizing illumination device according toclaim 9 47, wherein said optical attenuating device is a light diffusingsurface formed on a light emergent surface of said condenser lens array.16. The polarizing illumination device according to claim 8, whereinsaid device for preventing each of the intermediate beams from directlyentering said reflecting plane is integrated with said polarizingseparation element.
 17. The polarizing illumination device according toclaim 8 46, wherein said device for preventing each of the intermediatebeams from directly entering said reflecting plane is integrated withsaid condenser lens array.
 18. A display apparatus, comprising: a lightsource that emits a light beam; a first optical element that separatesthe light beam emitted from said light source into a plurality ofintermediate beams that converge at a converging position; a secondoptical element disposed at or near the converging position, the secondoptical element including: a condenser lens array that includes aplurality of condenser lenses that respectively condense theintermediate beams; a polarizing separation element that spatiallyseparates each of the intermediate beams into an S polarized beam and aP polarized beam, the polarizing separation element including a lightincident side, a light emergent side, a polarizing separation plane thatseparates P and S polarized beams by transmitting one of the P and Spolarized beams therethrough toward the light emergent side of thepolarizing separation element and reflecting the other of the P and Spolarized beams, and a reflecting plane disposed substantially parallelwith said polarizing separation plane that reflects the other of the Pand S polarized beams reflected by said polarizing separation planetoward the light emergent side of the polarizing separation element; aselective phase plate that aligns a polarization direction of one of theP and S polarized beams separated by said polarizing separation elementwith a polarization direction of the other of the P and S polarizedbeams, a superimposing lens that superimposes the polarized beams; and adevice for preventing each of the intermediate beams from directlyentering said reflecting plane interposed between said first opticalelement and said polarizing separation element; and a modulating devicefor modulating a light beam emitted from said second optical element.19. A projection display apparatus projector, comprising: a light sourcethat emits a light beam; a first optical element that separates thelight beam emitted from said light source into a plurality ofintermediate beams that converge at a converging position a secondoptical element disposed at or near the converging position, the secondoptical element including: a condenser lens array that indicates aplurality of condenser lenses that respectively condense theintermediate beams; a polarizing separation element that spatiallyseparates each of the intermediate beams into an S polarized beam and aP polarized beam, the polarizing separation element including a lightincident side, a light emergent side, a polarizing separation plane thatseparates P and S polarized beams by transmitting one of the P and Spolarized beams therethrough toward the light emergent side of thepolarizing separation element and reflecting the other of the P and Spolarized beams, and a reflecting plane disposed substantially parallelwith said polarizing separation plane that reflects the other of the Pand S polarized beams reflected by said polarizing separation planetoward the light emergent side of the polarizing separation element; aselective phase plate that aligns a polarization direction of one of theP and S polarized beams separated by said polarizing separation elementwith a polarization direction of the other of the P and S polarizedbeams; a superimposing lens that superimposes the polarized beams; and adevice for preventing each of the intermediate beams from directlyentering said reflecting plane interposed between said and first opticalelement and said polarizing separation element; at least one modulatingdevice for modulating a light beam emitted from said second opticalelement according to display information; and a projection opticalsystem for projecting the light beam modulated by said modulating deviceonto a projection plane.
 20. The projection display apparatus projectoraccording to claim 19, further comprising: color light separation systemfor separating the light beam into a plurality of colored lights; aplurality of said modulating devices for respectively modulating thecolored lights; and colored light synthesizing system for synthesizingthe colored lights modulated by said plurality of modulating devices;wherein a synthesized beam synthesized by said colored lightsynthesizing system is projected onto said projection plane through saidprojection optical system.
 21. The projection display apparatusprojector according to claim 19, wherein said at least one modulatingdevice is a reflection-type device.
 22. A method of converting randomlypolarized beams into substantially one type of polarized beams,comprising the steps of: separating P and S polarized beams with apolarizing separation element by transmitting one of the P and Spolarized beams through a separation plane of the polarizing separationelement toward a light emergent side of the polarizing separationelement, reflecting the other of the P and S polarized beams with theseparation plane, and reflecting the other of the P and S polarizedbeams reflected with the separation plane toward the light emergent sideof the polarizing separation element with a reflecting plane that isdisposed substantially parallel with the polarizing separation plane;aligning a polarization direction of one of the P and S polarized beamsseparated by the polarizing separation element with a polarizationdirection of the other of the P and S polarized beams with a selectivephase plate disposed at the light emergent side of the polarizingseparation element; and preventing light from directly entering thereflecting plane with at least one of a shading device and an opticalattenuating device.
 23. The method according to claim 22, wherein lightis prevented from directly entering the reflecting plane with areflecting plate.
 24. The method according to claim 22, wherein light isprevented from directly entering the reflecting plane with a reflectingfilm that is formed on a light incident surface of a light incident sideof the polarizing separation element.
 25. The method according to claim22, wherein light is prevented from directly entering the reflectingplane with a light diffusing plate.
 26. The method according to claim22, wherein light is prevented from directly entering the reflectingplane with a light diffusing surface formed on a light incident surfaceof a light incident side of the polarizing separation element.
 27. Apolarizing conversion device, comprising: means for separating P and Spolarized beams, including a separation plane, a reflecting plane, alight incident side and a light emergent side, by transmitting one ofthe P and S polarized beams through the separation plane toward thelight emergent side, reflecting the other of the P and S polarized beamswith the separation plane, and reflecting the other of the P and Spolarized beams reflected with the separation plane toward the lightemergent side with the reflecting plane; means for aligning apolarization direction of one of the P and S polarized beams separatedby the means for separating with a polarization direction of the otherof the P and S polarized beams; and means for preventing light fromdirectly entering the reflecting plane.
 28. The display apparatusaccording to claim 18, wherein the device for preventing each of theintermediate beams from directly entering said reflecting plane includesat least one of a shading device and an optical attenuating device. 29.The display apparatus according to claim 28, wherein said shading deviceis a reflecting plate.
 30. The display apparatus according to claim 28,wherein said shading device is a reflecting film and said reflectingfilm is formed on a light incident surface of the light incident side ofsaid polarazing separation element.
 31. The display according to claim50, wherein said shading device is a reflecting film and said reflectingfilm is formed on a light emergent surface of said condenser lens array.32. The display apparatus to claim 28, wherein said optical attenuatingdevice is a light diffusing plate.
 33. The display apparatus accordingto claim 28, wherein said optical attenuating device is a lightdiffusing surface formed on a light incident surface of the lightincident side of said polarizing separation element.
 34. The displayapparatus according to claim 50, wherein said optical attenuating deviceis a light diffusing surface formed on a light emergent surface of saidcondenser lens array.
 35. The display apparatus according to claim 18,wherein said device for preventing each of the intermediate beams fromdirectly entering said reflecting plane is intergrated with saidpolarizing separation element.
 36. The display apparatus according toclaim 49, wherein said device for preventing each of the intermediatebeams from directly entering said reflecting plane is integrated withsaid condenser lens array.
 37. The projector according to claim 19,wherein the device for preventing each of the intermediate beams fromdirectly entering said reflecting plane includes at least one of ashading device and an optical attenuating device.
 38. The projectoraccording to claim 37, wherein said shading device is a reflectingplate.
 39. The projector according to claim 37, wherein said shadingdevice is a reflecting film and said reflecting film is formed on alight incident surface of the light incident side of said polarizingseparation element.
 40. The projector according to claim 53, whereinsaid shading device is a reflecting film and said reflecting film isformed on a light emergent surface of said condenser lens array.
 41. Theprojector according to claim 37, wherein said optical attenuating deviceis a light diffusing plate.
 42. The projector according to claim 37,wherein said optical attenuating device is a light diffusing surfaceformed on a light incident surface of the light incident side of saidpolarizing separation element.
 43. The projector according to claim 53,wherein said optical attenuating device is a light diffusing surfaceformed on a light emergent surface of said condenser lens array.
 44. Theprojector according to claim 19, wherein said device for preventing eachof the intermediate beams from directly entering said reflecting planeis integrated with said polarizing separation element.
 45. The projectoraccording to claim 52, wherein said device for preventing each of theintermediate beams from directly entering said reflecting plane isintegrated with said condenser lens array.
 46. The polarizingillumination device according to claim 8, the sencond optical element,further comprising: a condenser lens array that includes a plurality ofcondenser lenses that respectively condense the intermediate beams. 47.The polarizing illumination device according to claim 46, the device toprevent each of the intermediate beams from directly entering saidreflecting plane including at least one of a shading device and anoptical attenuating device.
 48. The polarizing illumination deviceaccording to claim 8, the superimposing lens being a lens array thatincludes a plurality of lenses.
 49. The display apparatus according toclaim 18, the second optical element, further comprising: a condenserlens array that includes a plurality of condenser lenses thatrespectively condense the intermediate beams.
 50. The display apparatusaccording to claim 49, the device to prevent each of the intermediatebeams from directly entering said reflecting plane including at leastone of a shading device and an optical attenuating device.
 51. Thedisplay apparatus according to claim 18, the superimposing lens being alens array that includes a plurality of lenses.
 52. The projectoraccording to claim 19, the second optical element, further comprising: acondenser lens array that includes a plurality of condenser lenses thatrespectively condense the intermediate beams.
 53. The projectoraccording to claim 52, the device to prevent each of the intermediatebeams from directly entering said reflecting plane including at leastone of a shading device and an optical attenuating device.
 54. Theprojector according to claim 19, the superimposing lens being a lensarray that includes a plurality of lenses.